My invention relates to automotive vehicle suspension systems, and particularly to systems for the suspension of driving wheels which are maintained in parallel rotating planes by a dead axle.
For many years the driving wheels of many automotive vehicles were maintained in parallel planes by a dead axle housing which housed both the live axles connected to the driving wheels and the differential gears. The vehicle frame and body rested on springs supported on the dead axle housing inboard of the driving wheels and the wheel brakes.
While the foregoing suspension system was used for many years on many vehicles, it had a number of disadvantages. The necessity of vertical clearance between the differential housing and the underside of the body created loading problems for both passenger vehicles and heavier vehicles such as buses and trucks. Moreover, the combined weight of the dead axle housing, the differential, the live axles and a part of the drive shaft contributed to an undesirably high unsprung weight of the vehicle.
To overcome the deficiencies of the foregoing suspension system, many vehicles used a bowed dead axle as suggested in U.S. Pat. No. 562,289 to DeDion et al. DeDion type suspension systems and modifications thereof retained the advantage of a rigid connection between the driving wheels but had the additional advantage of lowering the floor of the vehicle's body because the minimum ground-to-floor distance was no longer dependent upon providing vertical clearance between the top of the differential housing and the body's floor.
However, the DeDion system has not been used on buses and heavier trucks because the bowed dead axle is subject to severe torsional stresses when resisting vertical displacement of the two driving wheels. Significant torsional displacement of the DeDion bowed dead axle produces unacceptable movements of the wheel axes and to eliminate such torsional deflection by increasing the size and weight of the bowed dead axle for buses and heavy trucks is both cost and design prohibitive.
My invention provides all the advantages of both the dead axle housing system incorporating the live axles and the differential gearing and the DeDion bowed dead axle system, while eliminating the disadvantages of these two systems. My improved suspension system reduces the vehicle's unsprung weight, substantially reduces the ground-to-floor distance of the body and provides a strong simple and inexpensive dead axle incapable of torsional displacement.
Briefly put, my unique driving wheel suspension system utilizes a straight cylindrical dead axle connecting a pair of wheel support assemblies, a body mounted differential, and universal jointed live axles connecting the driving wheels to the differential. Each wheel support assembly includes one or more leaf springs preferably with air springs mounted on its opposite ends and a wheel spindle support housing at its center. Preferably four suspension control rods are used to connect and control the position of the driving wheels, two to keep the wheel centered beneath the frame and/or body and two angled control rods to control lateral movement of the wheels. Shock absorbers are used to smooth out the ride of persons or cargo in the vehicle. In any event, my suspension system utilizes conical bearings at one or both ends of the straight dead axle which eliminate torsional loads being placed upon the dead axle by vertical displacements of the driving wheels.
By my system's elimination of the torsional loads which are imposed on all prior vehicle systems using dead axles, the weight and size of the dead axle can be markedly reduced since the dead axle need be designed to carry only the weight of the vehicle. The use of conical bearings at the ends of the dead axle eliminates the need for expensive and heavy bowed dead axles and constitutes the first major improvement in suspension systems for vehicle driving wheels since DeDion's bowed dead axle invention almost one hundred years ago.
The advantages of my vehicle suspension system for the vehicle's driving wheels include the following:
Because the dead axle can be designed to carry only the vehicle's weight, it is now possible to use a dead axle on heavy vehicles such as buses and trucks.
Reduction in the vehicle's unsprung weight.
Wider distances between left and right spring centers improves the vehicle's roll stiffness.
Passenger vehicles, vans, buses and light and heavy trucks can now all be designed with lower vehicle floors.
Increased ease of repair and replacement of parts. The dead axle, wheel spindle support housing, and leaf spring can be replaced simply by bolting in the replacement part. Moreover, the location of the dead axle to the rear of the live axles provides no interference with the repair or replacement of the power train from engine to live axles.
Because the dead axle lies to the rear of the differential housing, there are no cross members or a dead axle to interfere with the operation of the vehicles power train.